Composite material having a slide layer applied by cathode sputtering

ABSTRACT

For some applications of slide layers, for example in connecting rod bearings of internal combustion engines, for individual sites of a formed piece, high load bearing capability are required while for other places of the same formed piece good embedding abilities are demanded. A composite material with a slide layer applied by cathode sputtering of a tightly cohesive matrix and an insoluble component distributed statistically in it, is adapted to these opposite demands in that the diameter of the particle of the insolutble material has gradients at predetermined sites, which extend parallel to the surface of the slide layer, and to which slide layer hardness gradients correspond. These gradients are generated during the cathode sputtering process in the substrate to be coated to form a growing slide layer having temperature gradients which are maintained and which extend parallel to the substrate surface.

This is a divisional application Ser. No. 136,295, filed Dec. 22, 1987,now U.S. Pat. No. 4,889,772.

FIELD AND BACKGROUND OF THE INVENTION

The invention relates in general to sliding surface articles and inparticular to a composite material with at least one slide layer,applied by cathode sputtering, of a mixture of particles deposited instatistical distribution of at least one metallic material forming afirmly connected matrix and at least one additional metallic material,which in the solid state is practically insoluble in the matrixmaterial. It relates further to a method for manufacturing suchcomposite materials as well as use of the same in friction bearingshells.

As surface layers slide layers of composite materials are used, forexample, for bearing shells of internal combustion engines and must, inaddition to others, have the following properties: lower hardness thanthe material of the shaft, high strength with respect to alternatingdynamic stress, high shearing resistance, heat stability of themechanical properties as well as high corrosion resistance. Theserequirements are fulfilled, among others, by compositions of lead or tinwith metals, which lend the layer mechanical strength by forming acohesive matrix, they are themselves corrosion resistant and do notprocess solubility for tin or lead, like aluminum, chromium, or nickel,for example. Such composite materials having lead or tin containingslide layers as well as methods for their manufacture through cathodesputtering are described in German Pat. Nos. 28 53 724 and 29 14 618 aswell as in German No. OS 34 04 880.

When using such slide layers as surface layers, high opposite demandsare frequently made of the particular preform or machine part. Ifapplied for friction bearings they should, at least at particular sites,transfer the forces to which the bearing is subjected, with sufficientlong life, onto the surrounding structure (load bearing capacity) inorder to tolerate the surface pressure of the connecting rods. Thisrequires relatively high heat-stable hardness of the particular slidelayers and 70 HV 0.002 has been shown to represent a critical values,which should not be fallen below. Also, from other places of the samemachine part, particularly from its slide layers, good embeddingresponse is demanded, i.e. the ability to withstand embedding of dirt orwear and tear particles into the surface. Through such property thedanger of damage to the slide surfaces is decreased. In order to meetthis demand, the slide layers should not be too hard. Based onexperience, hardness of 70 HV 0002 represents also in this connection acritical value, which already requires relatively elaborate measures toprotect the particular bearing from entering dirt particles and to keepthe lubricant clean through filtration.

In the case of the slide layers described in the state of the artapplied by cathode sputtering such contradictory demands made of one andthe same machine or preform part cannot be met, since the slide layersin question have identical properties over their entire surface.

SUMMARY OF THE INVENTION

The present invention provides composite materials having slide layersapplied by cathode sputtering, which can fulfill optimum use fordifferent sites of the same machine, or preform operations with entirelyopposite demands regarding the material and in particular can combinegood embedding response at particular sites with good load bearingcapacities in others.

The task is solved through composite material according to theinvention, which has the following features:

The diameter of the particles of the material insoluble in the matrixhas at predetermined sites gradients (changes in values), which extendparallel to the surface of the slide layer. To these gradients of theparticular diameter (changes in the particular diameter) correspondgradients of hardness of the particular slide layer (changes in theparticular diameter).

The invention builds on the finding that the degree of hardness of aslide layer is a function of the particle size of the material insolublein the matrix and that a small particle diameter corresponds to a highdegree of hardness and a larger particle diameter to a lesser degree ofhardness. Therefore, if a slide layer is needed, which at given siteshas a high degree of hardness and correspondingly good load bearingability, at other sites a low degree of hardness corresponding to goodembedding capacity, then the particle size of the material insoluble inthe matrix must be varied appropriately, which can be effected bygenerating appropriate gradients of this particle size extendingparallel to the surface of the slide layer. For the mentioned materialcombinations (matrix: Al, Cr, Ni, insoluble: Sn, Pb) it has been shownto be of advantage, if the mean of the statistical normal distributionof the diameter of the insoluble particles varies in the region of thegradients between 0.2 μm and 10 μm. At those sites of the slide layer,at which highest load bearing capacity and correspondingly highesthardness is required, the diameter of the particles of the insolublematerial has advantageously a statistical normal distribution with amean value of x<0.8 μm, preferably within a range between 0.05<X<0.4 μm.This corresponds to an approximately ten times finer distribution of theparticles containing the insoluble material at the places of greatestload bearing ability compared to the layers disclosed in the state ofthe art. If for instance, AlSn2oCu produced by continuous casting, has ahardness of 35 HV 0.01, the layers according to the invention achieve atthese hardest sites a hardness of at least 180 HV 0.002 (cf. German Pat.No. 28 53 724, column 6). As to particulars, the invention is developedso that at the component insoluble in the matrix at least one of therelatively low melting elements tin (MP 231.89° C.), lead (MP 327.4° C.)can be utilized. For special applications, however, other low meltingmetals and their alloys are not excluded: cadmium (MP 320.9° C.),thallium (MP 302° C.), zinc (MP 419.5° C.), and even gallium (MP 29.8°C.). The invention yields particular advantages for composite materials,in which the matrix-forming component contains a conventional frictionbearing alloy, the primary components of which contain one of thefollowing elements: aluminum, chromium, nickel, magnesium, copper. Ithas been shown that it is particularly effective, if the slide layer asa whole has a composition with one of the following combinations:AlCuSn, AlCuPb, AlCuSnPb, AlSiSn, AlSiPb, AlSiSnPb, CuSn, CuPb, CuSnPb.Slide layers in accordance with the invention have preferentially layerthicknesses between 10 and 30 μm, with the lower half of this range (12to 16 μm), being satisfactory for most applications. The optimum layerthickness suggested by the state of the art for conventionaltwo-component slide layers of 18 m could not be confined in this respect(cf. U. Engel, in: SAE Technical Paper Series, International Congressand Exposition, Detroit 1986, page 76).

From the state of the art (German Pat. No. 29 14 618, column 5, GermanPat. No. 28 53 724, column 5) is further known, the oxide concentrationsbetween 0.1 and 0.5 volume percent in a so-called dispersion hardeningof the particular slide layers. In contrast, it has been demonstrated,surprisingly, that layers according to the invention, in the manufactureof which appropriate measures were taken (use of targets manufactured inan atmosphere of inert gases) to lower the oxygen concentration to lessthan 0.2 weight percent, at the sites having the smallest particlediameter of the insoluble components indicate significantly improvedmechanical properties compared to the known dispersion-hardened slidelayers. The approximately ten times finer distribution of theseparticles in the matrix of the slide layers hence replaces to someextent the hardening through dispersed oxide particles.

Surprisingly, it was found, that the slide layers according to theinvention in contrast to the layers disclosed in the state of the artreceive, through a combination of this, approximately a ten times finerdistribution of the insoluble component with an oxygen concentration inthe entire slide layer significantly increased tempering properties.While heat treatment for 300 hours at 170° C. with conventional slidelayers leads to a significant decrease of the degree of hardness (cf.German Pat. No. 28 53 724), the hardness at these sites of the layersaccording to the invention falls during such heat treatment only to anegligible extent. Through such combination the particular sites of theslide layer achieve with an approximately ten times finer distributionof the insoluble component and with 2.5 times the oxygen concentration ahardness of 100 HV 0.002.

In addition, these sites of the layers according to the invention showwhen compared to those disclosed in the state of the art, improvedtempering properties.

Through this high oxygen concentration in the layer extensive envelopingof the finely dispersed insoluble particles by O-atoms is achieved andthese decrease the danger, that these finely dispersed particlesre-aggregate through grain changes, in turn, to larger particles and inthis way the advantageous properties of the slide layers according tothe invention are partially lost through aging. The conditions at thetime the slide layer was generated are, in other words, stabilized bysuch high oxygen concentrations in the course of time. On thisconnection rests the substantially increased strength, compared toconventionally oxygen-doped layers--of the slide layers according to theinvention under alternating dynamic stress as well as the increased heatresistance of the mechanical properties of these layers. Here must beconsidered that for effective enveloping of very finely distributedparticles, with correspondingly large total surface area, more oxygenatoms are required than for enveloping the same mass more coarselydistributed and having a correspondingly smaller total surface area.

Corresponding to the specific function of the preformed part to becoated, the hardness gradients and thus the sites of differing hardnessof the slide layer according to the invention, can be distributed in anygeometric configuration over the entire surface of the slide layer. Inmany applications, annular zones of extremely high hardness arerequired, which demand corresponding hardness gradients of annularoutline, in which the areas of greatest hardness lie in the interior ofthe annulus.

The invention relates further to a method for manufacturing thesuggested composite materials, in which the slide layer is applied bythe cathode sputtering method. The task in this part of the inventionconsisted in generating gradients of the diameter of the insolubleparticles in the slide layer and thus gradients of hardness of it withgood reproducibility in any geometric configurations and within thelargest possible range of the variation of particle diameterrespectively surface hardness.

This task is solved according to the invention, in that during theprocess of cathode sputtering temperature gradients are generated in thesubstrate to be coated and in the corresponding slide layer itself andmaintained, which extend parallel to the surface of the substrate. Suchtemperature gradients can advantageously be generated in that thesubstrate to be coated during the cathode sputtering process is stronglycooled at different sites with the greatest cooling capability broughtabout at those sites, at which the slide layer is intended to havesmallest the particle diameter and the greatest hardness. Thetemperature of the substrate to be coated and the growing slide layersis kept advantageously throughout the process within a range between-10° and 190° C., that of the site, at which smallest particle diameterand greatest hardness of the slide layer is sought between -10° and +70°C. This approach is based on the surprising findings, that a decrease ofthe substrate temperature during cathode sputtering leads to anunexpected large decrease of the mean diameter of the particlesinsoluble in the matrix and therefore to a corresponding increase of thehardness of the slide layer at the particular sites, which goes hand inhand with fatigue limit under reversed stress and corrosion resistance.

Apart from this reduction of the coating temperatures an increased,coating rate over 0.2 μm/minute contributes to the fine distributionaccording to the invention of the insoluble component. This connectioncan be specifically exploited in those situations, in which insufficientquantities of cooling water for carrying out the method is available.This method provides that the different materials of the slide layer,thus, specifically the material forming the matrix and the one insolublein the matrix are applied simultaneously through cathode sputtering onthe substrate, which, in addition, improves the fine distribution of theinsoluble component according to the invention. This can be accomplishedpreferentially in that more than half the targets used in the processcontain the primary component of the matrix as well as the materialinsoluble in the matrix. Corresponding to the composition of the desiredslide layer, specifically alloys with the following composition can beused: AlCuSn, AlCuPb, AlSiSn, AlSiPb, AlSiSnPb, CuSn, CuPb, CuSnPb.

In another modification of the method the different component of theslide layer are applied on the substrate time-sequentially. For this,advantageously targets of the main components of the slide layer, forexample, pure aluminum and pure tin are employed and sputtered atdifferent positions of the particular coating device. Particularlyeffective can be the use for generating the diffusion blocking layer andthe slide layer the same targets and to form the two different layersimmediately one after the other on the workpieces to be coated. In afurther variant of the method according to the invention the temperatureof the substrate is varied in the sense, that the matrix-formingcomponent is applied at higher temperatures than the component insolublein the matrix. In a further variant this can take place in such a waythat the matrix-forming component of the slide layer is applied atincreased substrate temperatures preceding that of the insolublecomponent and the temperature during the coating process is decreased.Further possibilities for varying the method according to the inventionresult from the fact, that the voltage which is applied to the substrateto be coated is varied corresponding to the given requirements of theconcrete application. This can best be carried out in that thecomponents with the highest melting points, perhaps the matrix-formingcomponent or the primary component of the diffusion blocking layer, isapplied at a higher voltage than the component insoluble in the matrixwith the lower melting point. The oxygen required for oxygen doping canbe introduced either in the form of a gaseous substance during theprocess of cathode sputtering into the plasma gas or before the cathodesputtering process in the form of oxides of the elements contained inthe matrix-forming materials in the target utilized for this purpose ora part of the target used here. In the first case the gaseous substancesto be used are primarily elemental oxygen itself or air, although inparticular applications oxygen compounds of one of the followingelements or of combinations of these elements can be utilized: hydrogen,carbon, nitrogen. Of these oxygen compounds water vapor and CO₂ haveprobably the greatest practical significance for the here discussedoxygen doping. Customarily, in this variant during the coating processthrough cathode sputtering in the vacuum changer of the device, apartial pressure of the oxygen-supplying gas of 1 to 50% of the totalpressure of the gas mixture is maintained with argon beingpreferentially used as further component of this mixture.

According to a second variant the oxygen required for the specificapportioning is deposited a oxide in the target used for cathodesputtering or a part of the utilized target. This offers the possibilityof controlling the degree of oxygen doping of the slide layer over thisoxide content of the target or over the electrical power density of itduring the cathode sputtering. This can specifically take place in thatthe particular target for the purpose of setting the requisite oxygenconcentration is subjected before the cathode sputtering to acombination of vacuum and heat treatment in an oxygen-containingatmosphere. An alternative method consists in the specific addition ofoxide powder, for instance Al₂ O₃, in the manufacture of the targets, beit in continuous casting or by way of pressing and sintering pulverizedmetals. In accordance with the preferred matrix-forming materials theseare primarily the oxides of the following elements: aluminum, chromium,nickel, magnesium, copper, tin, indium, lead, zinc.

The composite materials according to the invention can be successfullyemployed in friction bearings of any kind. The bearing shells used insuch slide layers are provided with the slide layers according to theinvention as surface layers such that this slide layer at the top of thebearing shell has the smallest mean particle diameter of the insolublecomponent and hence the greatest hardness and in the region of the seamwith the matching shell the largest mean particle diameter and hence theleast hardness. At the top of the bearing shell the slide layer musthave a hardness of more than 100 HV 0.002, in order to absorb thesurface pressures of the connecting rods. Slide layers according to theinvention can be used for bearing loads between 80 and 120N/mm² and attemperatures of the bearing back between 150° and 200° C. Under theseconditions the layers according to the invention did not show anymeasurable wear and tear after continuous load testing for 720 hours.

Accordingly it is an object of the invention to provide a compositematerial which has at least one cathode sputtering applied slide layerof a mixture of particles deposited in a statistical distribution of atleast one tightly cohesive metallic material forming a matrix and atleast one additional metallic material in a solid state which issubstantially insoluble in the matrix material and with the diameters ofthe particles of the metallic material which are insoluble in the matrixhaving gradients at predetermined locations which extend parallel to thesurface of the slide layer and to which correspond gradients of thehardness of the slide layer.

A further object of the invention is to provide a method ofmanufacturing composite materials by cathode sputtering with at leastone slide layer of a mixture of statistically distributed particles ofat least one material performing a matrix material and at least oneadditional material insoluble in the matrix material which comprisesmaintaining layer temperature gradients while cathode sputtering to forma slide layer which grows on the substrate to be coated and wherein thetemperature gradients are maintained so as to extend parallel to thesurface of the substrate.

A further object of the invention is to provide a use of compositematerials such as set forth in the method in a friction bearing shellparticularly for dynamically high stressed bearing.

A further object of the invention is to provide a bearing or similarslide layer which is simple in design, rugged in construction andeconomical to manufacture.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic perspective view of a formed part of the compositematerial according to the invention;

FIG. 1A and FIG. 1B are microscopic hardeners gradient views atlocations A and B of FIG. 1;

FIG. 2 is a cross section through a radial friction bearing (connectingrod bearing) of a high-speed internal combustion engine with bearingshells of the composite material according to the invention; and

FIG. 3 is an enlarged axial sectional view of the shaft bearing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in particular, the invention relates toarticles which have sliding surfaces and to a composite material havinga slide layer which is applied by cathode sputtering.

In the model of FIG. 1, on a steel back (base material) 1 a carrierlayer 2 of a material having good emergency running properties of layerthickness from 200 to 700 μm is applied. If for this carrier layer 2 alead or lead/tin bronze is used, this layer has a hardness between 50and 100 HV 0.002. Onto this carrier layer 2 a thin diffusion blockinglayer 3 having a layer thickness of customarily a few μm (2-4 μm) isapplied through cathode sputtering. This diffusion blocking layercomprises one or several elements of the matrix-forming material of theslide layer, for example, nickel, chromium, or an alloy thereof. Ontothis blocking layer 3 the slide layer 4 according to the invention isapplied through cathode sputtering. The particle size of the insolublecomponent differing due to the temperature gradients during the cathodesputtering process is shown in the enlarged details A and B, withSection A corresponding to a finely distributed part with high surfacehardness, section B a part with greater mean particle size andcorrespondingly decreased surface hardness. Accordingly, the hardnessgradient in slide layer 4 extends from section A to section B.

In FIG. 2 use of the composite material according to the invention asbearing shells in a radial friction bearing (connecting rod bearing) ofa high-speed internal combustion engine is shown. The connecting rod 11converts its motion into a rotational motion of a crankshaft, consistingof crankshaft journal 12, journal 13 and two different crank arms 14 and15. Between the split lower connecting rod big end 16 and the rotatingcrankshaft journal 12 two semi-cylindrical bearing shells of thecomposite materials according to the invention are set in and the fitsecured with the connecting rod screws 17. The slide layer 4 of thebearing shells, consequently, is in contact with the crankshaft journal12 and the steel back 1 rests on the connecting rod big end 16.

In this arrangement, sections A at the top of the bearing shells needhigh load bearing ability in order to absorb the surface pressure of theconnecting rod, and therefore have a fine distribution of the insolublephase as shown in FIG. 1. In contrast, of section B at the transition tothe matching shell good embedding properties for abrasion and dirtparticles are demanded, which can be achieved through appropriate lessersurface hardness and coarser distribution of the insoluble component. Inboth bearing shells, consequently, two hardness gradients according tothe invention each exist between sections A and B.

For generating the composite material according to the invention, forexample, the following reaction conditions were maintained:

EXAMPLE 1

Coating was carried out in a cathode sputtering device known per se, inwhich an annular dense plasma was concentrated with a magnetic fielddirectly before the cathode. The installation had a cylindrical processchamber, at the outside of which up to a maximum of four sources of322.6 cm² could be vertically mounted. The substrates to be coated werelikewise placed vertically on a carrier, which could be rotated by adrive variable between 0.2 and 24.5 rotations per minute (cf. forexample,. BALZERS Produktinformation BB 800 246 PD/Aug. 1985 as well asBB 800 039 RD/July 1985).

Bearing shells of non-alloyed tool steel (material No. 1.1625, short(80W2) having a lead bronze (CuPb 23Su4) carrier layer of 200 μm appliedin sintering process were coated in this sputtering installation at apressure of 1.2 Pa in argon under complete absence of oxygen for 8hours. A separate cooling line took care that the top (section A inFIG. 1) was cooled exclusively. This measure produced at this place asubstrate temperature of 30° C., while the temperature in the directionof section B of the bearing shell increased and at both ends of thebearing shell was between 170° and 190° C. To maintain this temperatureat the top of the bearing shells 0.005 m³ cooling water (˜10° C.) wasrequired per hour and per bearing shell to be coated.

As targets, on the one hand, pure aluminum (99.99) was used at a voltageof 470 Volt, on the other hand, a tin bronze of composition SnCu5 at avoltage of 620 Volt was used and run with a power density of 20 kW/322cm² respectively of 10.3 kW/322 cm². Upon rotation of the substrate at aconstant rate of rotation of 15 rotations per minute, a coating rate ofapproximately 0.3 m/Min corresponding to a layer thickness ofapproximately 150 m was achieved at the end of the treatment.

The layer generated in this manner had a weight ratio of Al:Sn:Cu of80:20:1 (corresponding to the composition AlSn20Cul) and an oxidecontent of less than 0.2 weight percent. At the bearing top a meanparticle diameter of approximately 0.3 m and at the ends of the bearinqshells one of approximately 5 m was obtained. The hardness was 113 HV0.002 at the bearing top (section A) and 45 HV 0.002 at the ends of thebearing shells (section B). This hardness decreases upon exposure to airat 170° C. for 250 hours only to approximately 92 HV 0.002. When testedon the bearing testing machine for 250 hours, a load of 70N/mm² and abearing back temperature of T=160° C. these layers showed no measurablewear and tear.

EXAMPLE 2

The processing conditions of Example 1 were varied in the sense thatinitially for 11/2 hours only the targets of an AlSi alloy (Al+0.1-2%Si) were turned on and the bearing shells cooled to a uniformtemperature of 120° C. Subsequently, the two other targets of the tinbronze were connected and the cooling set so that it fell at the top ofthe bearing shells to 20° C., at the ends of the bearing shells to 80°C. The remainder of the coating process was carried out under theconditions given in Example 1.

It yielded a hardness of the slide layer at the bearing top (section A)of 130 HV 0.02 and one of 45 HV 0.02 at the two ends of the bearingshells (section B).

EXAMPLE 3

The processing conditions of Example 1 were modified in that in theprocess chamber of the cathode sputtering installation a pressure of 1.2Pa in the argon was maintained, to which 5.0 volume percent oxygen wasadded. In contrast to the layer obtained according to Example 1, thelayer generated under these conditions had an oxygen content of 1.89weight percent. To this corresponded a hardness of 160 HV 0.002 at thebearing top (section A in FIG. 1) and one of 35 HV 0.002 at the edges ofthe shell (section B in FIG. 1. The response of the layer during testingon the bearing test machine corresponded to that of the slide layerproduced in Example 1.

EXAMPLE 4

Bearing shells of the same tool steel (material No. 1.1625) having a 200m thick carrier layer of CuPb23Sn4 (lead bronze) applied by immersionwere coated in the absence of oxygen in the plasma gas under the samecondition as in Example 1. The quantity of water here w as 0.035 m³ perhour and per bearing shell to be coated. To apply the slide layer thefollowing targets and power densities were used: a target tin (10.3kW/322 cm²), a target lead (11 kW/322 cm²) as well as 2 targets AlSiwith changing concentrations of Al₂ O₃ (1-5 weight percent) and changingelectrical power density (20-120 kW/322 cm²).

This yields a slide layer of the approximate composition AlSi45Sn15Pb20,the oxygen content of which could be set by varying the oxide content aswell as the electrical power density of the target during the sputteringprocess. When two targets were used with an oxide concentration of 5%Al₂ O₃ at a power density of 20 kW/322 cm², for example,. a finalconcentration of 0.7 weight percent oxygen in the layer was obtained, atone of 80 kW/322 cm² an oxygen concentration of 1.2 weight percent wasobtained. These layers had at the top of the bearing shells a meanparticle diameter of 0.2 μm and at the edges of it one of 5 μm. Theirhardness accordingly was between 165 HV 0.002 (section A) and 50 HV0.002 (section B).

EXAMPLE 5

The process conditions of Examples 1 to 4 can be varied so that thebearing shells before the application of the slide layer are providedwith a thin diffusion blocking layer (FIG. 1: position 3). For thispurpose only the two targets of the AlSi alloy are turned on (20 KW/322cm²) for 12 minutes and at 30° C. The layer thickness of the diffusionblocking layer generated in this way was approximately 2 μm.Subsequently, the other targets are connected and the coating completedunder the same conditions as in Examples 1 to 4.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:
 1. A method of manufacturing a composite material,comprising the steps of: applying by cathode sputtering a slide layersurface of a mixture of particles deposited in a substantiallypredetermined distribution of at least one cohesive metallic materialforming a matrix and at least one additional metallic material in thesolid state, said additional metallic material defining particles,substantially insoluble in the matrix material; and, generating meanparticle diameter gradients of said particles to provide locations ofparticles of small mean diameter, of high hardness and good load bearingability, and to provide locations of particles of larger mean diameterwith a lower degree of hardness, of good embedding capacity.
 2. A methodaccording to claim 1, wherein said step of generating mean particlediameter gradients comprises reducing coating temperatures at specificlocations during said step of cathode sputtering.
 3. A method accordingto claim 1, wherein said reduced temperatures are maintained so as toextend parallel to the surface of the substrate.
 4. A method as statedin claim 2, wherein the reduced temperatures are generated in a mannersuch that the substrate to be coated is, during the cathode sputteringprocess, cooled in different locations to a different degree with thegreatest cooling capability being produced in those sites, at which theslide layer is intended to have the smallest particle diameter and thehighest degree of hardness.
 5. A method of manufacturing a compositematerial according to claim 1, wherein said step of generating meanparticle diameter gradients comprises increasing the coating rate over0.2 μm/min. to provide said locations of locked particles of small meandiameter.
 6. A method of manufacturing a composite material according toclaim 1, wherein said step of generating a mean particle diametercomprises applying said metallic material forming a matrix and saidadditional metallic material on the substrate, timed sequentially.
 7. Amethod according to claim 1, wherein said step of generating meanparticle diameter gradients comprises applying said metallic materialforming a matrix at a first temperature and applying said additionalmetallic material at a second temperature which is lower than said firsttemperature.
 8. A method according to claim 1, wherein the temperatureof the substrate to be coated and the growing slide layer is maintainedbetween -10° and 190° C.
 9. A method according to claim 1, wherein thetemperature of the substrate to be coated and that of the slide layer atwhich the smallest particle diameter and the highest degree of hardnessof the slide layer is to be obtained is maintained between -10° and 70°C.
 10. A method as stated in claim 1, wherein different components ofthe slide layer are applied simultaneously.
 11. A method according toclaim 1, wherein different components of the slide layer are introducedinto the slide layer over a period of time.
 12. A method according toclaim 1, wherein the metallic material forming matrix is applied beforethe additional metallic material and the temperature of the substrate isuniformly decreased during the coating process.
 13. A method accordingto claim 1, wherein oxygen is supplied to the plasma during the cathodesputtering in the form of a gaseous substance.
 14. A method according toclaim 1, wherein oxygen is deposited as an oxide on the target used forcathode sputtering.
 15. A method of manufacturing a composite material,comprising the steps of: applying a slide layer surface to a substrateby cathode sputtering the slide layer surface being formed of a mixtureof particles deposited in a substantially predetermined distribution ofat least one cohesive metallic material forming a matrix and at leastone additional metallic material in the solid state, said additionalmetallic material defining particles, substantially insoluble in thematrix material; and, generating mean particle diameter gradients ofsaid particles to provide locations of locked particles of small meandiameter, of high hardness and good load bearing ability, and to providelocations of particles of larger mean diameter with a lower degree ofhardness, of good embedding capacity wherein the temperature of thesubstrate and that of the growing slide layer at which the smallestparticle diameter and the highest degree of hardness of the slide layeris to be obtained, is maintained between -10° and 70 ° C.